1. Field of the Invention
The present invention relates to a leveling machine for steel sheet and strip, particularly for cold-rolled steel sheet and strip. The leveling machine includes upper and lower leveler rolls which are arranged offset relative to each other and are supported along their length by means of support rollers mounted in bearing blocks. The support rollers, in turn, are supported in crossheads, wherein at least the upper crosshead is adjustable for positioning the leveler rolls Changing cartridges are arranged between the crossheads and the leveler rolls for exchanging a set each of leveler rolls and support rolls. The changing cartridges are of an articulated construction, so that the support rollers can be preadjusted in groups on the two sides of the middle vertically extending transverse plane of the crossheads and leveler rolls. The preadjustment serves to compensate the sagging of the leveler rolls while taking into consideration the bending of the crossheads due to the leveling force, so that the leveler rolls are straight during leveling.
2. Description of the Prior Art
Leveling machines of the above-described type are known and provide so-called tilting yoke adjustment. Leveling machines of this type have upper and lower transverse yokes or crossheads and changing cartridges which are divided in the middle vertically extending transverse plane of the leveler rolls and are articulated by means of articulated joints in such a way that the portions of the crossheads and cartridges including the groups of support rollers for the leveler rolls supported by the cartridges are slightly tilted or adjusted in the shape of a V under idle running conditions. When the leveling force becomes effective, the crossheads and changing cartridges are supposed to bend until the preadjusted V-shape disappears and the groups of support rollers are in axial alignment and, thus, the leveler rolls are straight. As a result, the sagging of the crossheads is compensated.
Of course, the crossheads or at least the upper crosshead as a whole are obliquely adjustable in feeding direction of the material to be leveled by means of two pairs of adjusting devices supported in stands. Accordingly, the depth of immersion of the offset leveler rolls can be decreasingly adjusted from the entry side of the material to be leveled to the exit side in order to obtain an overstretching distribution.
The sagging behavior of divided crossheads of known steel sheet leveling machines with the above-described tilting yoke adjustment is determined by the fact that the crossheads are to be considered girders having two supports, wherein the bending forces act at least initially in the middle plane of symmetry until the leveler rolls are straight due to the bending or sagging of the crossheads. Thus, an optimum sagging is achieved at a predetermined bending stiffness of the crossheads. However, the extent of the preadjusted V-shape of the divided crossheads is also dependent upon the degree of sagging. Since, moreover, the leveler rolls should under idle running conditions already rest against the groups of support rollers which are also aligned in a V-shape, the leveler rolls must also be pre-bent into a V-shape by means of forces acting at the ends thereof. Since, due to the significant tilted position of the groups of support rollers to the left and right of the middle vertically extending transverse plane of the crossheads, the leveler rolls must be prebent to a significant degree, the leveler rolls are subjected to substantial bending forces until they become straight as a result of the leveling forces.
It is, therefore, the primary object of the present invention to improve the above-described known tilting yoke adjustment in a leveling machine for steel sheet and strip, so that the leveler rolls must be prebent to a lesser extent prior to the occurrence of the leveling force. Thus, the leveler rolls are to be subjected to a more careful treatment during operation.